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SCH. 40 vs ABS

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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SCH. 40 vs ABS

Unread postAuthor: 8tonsemi » Thu May 24, 2012 1:45 pm

I want your opinion on what you think is better for an advanced spud gun. Run of propane or mapp gas. Sorry this is kind of a nooby question. :lol:

Oh and does Abs really crack instead of explodeing.
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Unread postAuthor: budabob07 » Thu May 24, 2012 1:49 pm

I've heard that ABS cracks instead of exploding and shooting shrapnel everywhere so it would probably be safer. SCH 40 is much more common though.
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Unread postAuthor: 8tonsemi » Thu May 24, 2012 1:51 pm

Where I live I can get ABS everywhere
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Unread postAuthor: mattyzip77 » Thu May 24, 2012 2:02 pm

If your going to spend the money on a b s, why not just spend a few bucks more on steel??? I have never used a b s on a spud gun, however I heard from multiple forum members that it is alot safer than p v c.
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Unread postAuthor: Technician1002 » Thu May 24, 2012 2:15 pm

Sched 40 is a size definition. ABS is a plastic material. PVC is a plastic material. Both ABS and PVC can be purchased in Sched 40 size. Steel can be purchased in Sched 40 size.

On to materials.. I have a thread on the subject. Search could have found it.

http://www.spudfiles.com/forums/pvc-is-fragile-t21334.html

In testing ABS..
http://www.spudfiles.com/forums/is-this-safe-to-use-t20954.html

http://www.spudfiles.com/forums/abs-cellular-core-test-cannon-t17968.html

http://www.spudfiles.com/forums/abs-cannon-explosion-t8573.html

A photo of an ABS failure with a more than normal pressure.
Image

DANGER.. Do not try this at home. Please do not use Oxygen in your cannons. Oxygen is what caused the above damage. Link for material failure mode only. ABS should be fine for normal metered propane.
http://www.sentex.net/~mwandel/cannon/my_cannon.html
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Unread postAuthor: 8tonsemi » Thu May 24, 2012 2:41 pm

I actually have read your thread its great. I meant this to be more of a poll
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Unread postAuthor: MrCrowley » Thu May 24, 2012 3:50 pm

Well we already have had loads of topics like this one (that poll people's opinions on the matter). If you can find pressure rated ABS, by all means use that instead of PVC. If you can find DWV ABS (non-cell core), it will be fine on a properly constructed combustion cannons. I would recommend pressure rated ABS or pressure rated PVC for pneumatics but ABS would be the better option.

As for an advanced combustion (propane or MAPP) DWV ABS probably can be used reasonably safely, just make sure to tap any fittings in to double layered areas (where a pipe meets a fitting, for example).
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Unread postAuthor: 8tonsemi » Thu May 24, 2012 4:43 pm

Thank you for the help. :lol:
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Unread postAuthor: boyce123 » Sun Jun 03, 2012 10:51 pm

Image
this is the only picture of a failure i've ever seen come up (besides the occasional end cap blowing up), can anyone find what a full chamber failure looks like, with abs or pvc?
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Unread postAuthor: Crna Legija » Mon Jun 04, 2012 1:13 am

PVC will turn to shrapnel, abs just a single crack like above.
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Unread postAuthor: MrCrowley » Mon Jun 04, 2012 1:21 am

I've had some fittings on a PVC chamber fail at around 100PSI. With three people around it, no one was hurt but I owe that to the fact it was down by our waists and not close to our faces. It does indeed shrapnel.

With your proposed hybrid chamber, you would probably be better off just using the copper piping you planned to use as a sleeve and fibre glassing it.
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Unread postAuthor: jackssmirkingrevenge » Mon Jun 04, 2012 1:36 am

MrCrowley wrote:Well we already have had loads of topics like this one (that poll people's opinions on the matter).


This is science, opinions shouldn't matter - only cold hard facts ;)
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Unread postAuthor: MrCrowley » Mon Jun 04, 2012 1:51 am

Well I say opinions because the facts aren't in question, it is how we choose to interpret them. This of course is aimed at the argument over whether we should use PVC or not due to its failure characteristics and manufacturer warnings about using it with pressurised air (which is essentially about failure characteristics). I think whether one should follow that warning or not is a matter of opinion. :P

If anyone has missed out on such an argument, it goes like this:
Person A: If your PVC chamber fails, it will shrapnel with potentially harmful consequences.
Person B: Well it's a good thing then that my chamber is rated for 260PSI and I only use it at 120PSI.
Person A: The same people who put a rating on that pipe also state that it shouldn't be used with pressurised air.
Person B: Well that's because of the failure characteristics, not because air is harmful to the structural properties of the pipe.


Rinse and repeat. :D
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Unread postAuthor: jackssmirkingrevenge » Mon Jun 04, 2012 2:11 am

MrCrowley wrote:I think whether one should follow that warning or not is a matter of opinion. :P


Fair enough, the question is do we have enough data to make an informed choice? Massive subtle hint wink wink nudge nudge :)
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Unread postAuthor: boyce123 » Mon Jun 04, 2012 4:49 pm

MrCrowley wrote:With your proposed hybrid chamber, you would probably be better off just using the copper piping you planned to use as a sleeve and fibre glassing it.


i'm not sure if this was directed at me, but i'll reply, i was actually thinking of making an all copper chamber, then i remembered that i don't have any 3" copper fittings, and 3" copper fittings are expensive... this (http://www.spudfiles.com/forums/new-hyb ... 24270.html) was meant to be as cheap as possible... but back the the topic on hand. I know what how the pvc is supposed to fail, but i've never seen pictures of a chamber failure. Curiosity led me to wonder the shrapnel size, power, and spread pattern in the case of a full chamber pvc failure.
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